L-Carnitine Tartrate Supplementation for 5 Weeks Improves Exercise Recovery in Men and Women: A Randomized, Double-Blind, Placebo-Controlled Trial

Abstract

L-carnitine tartrate has been shown to improve relatively short-term recovery among athletes. However, there is a lack of research on the longer-term effects in the general population.

Objective: The primary objectives of this randomized double-blind, placebo-controlled trial were to evaluate the effects of daily L-carnitine tartrate supplementation for 5 weeks on recovery and fatigue.

Method: In this study, eighty participants, 21- to 65-years-old, were recruited. Participants were split into two groups of forty participants each, a placebo, and a L-carnitine Tartrate group. Seventy-three participants completed a maintenance exercise training program that culminated in a high-volume exercise challenge.

Results: Compared to placebo, L-carnitine tartrate supplementation was able to improve perceived recovery and soreness (p = 0.021), and lower serum creatine kinase (p = 0.016). In addition, L-carnitine tartrate supplementation was able to blunt declines in strength and power compared to placebo following an exercise challenge. Two sub-analyses indicated that these results were independent of gender and age. Interestingly, serum superoxide dismutase levels increased significantly among those supplementing with L-carnitine tartrate.

Conclusions: These findings agree with previous observations among healthy adult subjects and demonstrate that L-carnitine tartrate supplementation beyond 35 days is beneficial for improving recovery and reducing fatigue following exercise across gender and age.

Keywords: L-carnitine tartrate; carnitine; exercise; fatigue; muscle damage antioxidant; muscle power; muscle strength; recovery.

Figure 1

CONSORT flow diagram. CAR: L-carnitine group; PLA: placebo.

Figure 2

Serum creatine kinase (CK) concentration. Mean values and error bars for the standard error of the mean for concentration values of serum creatine kinase (CK) are shown. * indicates a significant difference between the time point Pre and Wk5-Post (p < 0.001). ^ indicates a significant difference between groups (p < 0.05). The groups are carnitine (CAR) and placebo (PLA).

Figure 3

Relative perceived recovery status. Mean values and error bars for the standard error of the mean for perceived recovery values normalized to training volume for the muscle damaging protocol are shown. The following equation was deployed to reach the arbitrary units (au): (Post Exercise PRS - True Baseline Pre)/total repetitions) × 100; * indicates a significant difference between groups (p < 0.05). The groups are carnitine (CAR) and placebo (PLA). Abbreviations: au—arbitrary units.

Figure 4

Serum carnitine concentration. Mean values and error bars for the standard error of the mean for concentration values of total serum carnitine concentration are shown. # indicates a significant difference from the time point Pre (p < 0.001). * indicates a significant difference between groups (p < 0.001). The groups are carnitine (CAR) and placebo (PLA).

Figure 5

Serum superoxide dismutase (SOD). Bar chart for the mean values and error bars for the standard error of the mean for serum super oxide dismutase (SOD) are shown. * indicates a significant difference from Pre (p < 0.001). The groups are carnitine (CAR) and placebo (PLA).

Figure 6

Maximum relative power output delta. Mean values and error bars for the standard error of the mean for the relative delta change (Time₂ − Time₁), from Wk5-Pre to Wk5-Post, of power output from the countermovement jump (CMJ) and squat jump (SJ) are shown; * indicates a significant difference between groups (p < 0.05). The groups are carnitine (CAR) and placebo (PLA).

Figure 7

Maximal isometric strength delta. Mean values and error bars for the standard error of the mean for the relative delta change (Time₂ - Time₁), from Pre to Wk5-Post and Wk5-Pre to Wk5-Post, of strength output of the isometric midthigh pull are shown; * indicates a significant difference between groups (p < 0.05). The groups are carnitine (CAR) and placebo (PLA).

Figure 8

Serum C-reactive protein (CRP). Mean values and error bars for the standard error of the mean of serum C-reactive protein (CRP) levels are shown. # indicates a significant difference from Pre (p < 0.001). * indicates a significant difference from Wk5-Post (p < 0.005). ^ indicates a significant difference between groups (p < 0.001). The groups are carnitine (CAR) and placebo (PLA) [21].

Figure 9

CK (A), SOD (B), and carnitine (C) ΔCAR vs. ΔPLA (95% CI). The 95% confidence intervals of the between group difference for the relative change from Wk5-Pre to Wk5-Post (∆CAR vs. ∆PLA) by age and gender groups for CK (A), and the between-group difference for the relative change from Pre to Wk5-Post (∆CAR vs. ∆PLA) by gender and age groups for SOD (B) and carnitine (C) are shown. The groups are carnitine (CAR) and placebo (PLA). Abbreviations: CK = creatine kinase; SOD = superoxide dismutase.

Figure 10

Performance metrics ΔCAR vs. ΔPLA (95% CI). The 95% confidence intervals of the between-group difference are shown for the relative change from Wk5-Pre to Wk5-Post (∆CAR vs. ∆PLA) by gender and age for IMTP (A), SJ (B), and CMJ (C). The groups are carnitine (CAR) and placebo (PLA). Abbreviations: IMTP = isometric mid-thigh pull; SJ = squat jump; CMJ = countermovement jump.

Figure 11

Changes in serum carnitine levels during the menstruation cycle from pre-menstruation are shown. * indicates statistical significance between groups (p < 0.001). The groups are carnitine (CAR) and placebo (PLA). Abbreviations: MC = menstrual cycle; NMC = non-menstrual cycle.